Most of the Jedi, most of the planets, the plots as a whole would have worked fine if they'd been executed better. The problem was there was no tension and no second writter to tell George he needed to explain things better or he was making plot holes. Most characters work very well outside of the films look at this, Grievous was awesome bother Episode III came out:

EDIT:

It's a shame what's become of such a cool character, I don't know whats worse the fact he can barely hold his own with the gungans or that god awful dialogue.